ANS:A - semi-conductor

With an increase in temperature, the electrical conductivity of a semiconductor generally increases. In metals and alloys, the electrical conductivity typically decreases with an increase in temperature due to increased scattering of charge carriers by lattice vibrations (phonons). This phenomenon is known as the temperature coefficient of resistivity, and it results in a gradual increase in resistivity and a decrease in conductivity as temperature rises. However, in semiconductors, the behavior is different. As temperature increases, more electrons are thermally excited from the valence band to the conduction band, increasing the number of charge carriers and thus the conductivity. This phenomenon is described by the intrinsic carrier concentration and is responsible for the positive temperature coefficient of resistance observed in semiconductors. Therefore, the correct statement is: With an increase in temperature, the electrical conductivity of a semiconductor generally increases.